Adaptive QoS for
Multimedia Applications in Heterogeneous Networks
To enable multimedia
applications in heterogeneous network environment by providing policy based
adaptive QoS mechanism
The overall objective of
this project is to design and implement an adaptive Quality of Service (QoS)
management framework for multimedia applications in distributed heterogeneous
environments. The goal of this framework is to automatically adapt application
and system operation, based on current client, system and network state, to meet
end-to-end quality of service requirements. Adaptation is performed both at the
application level as well as at the network level. The driving application
domain is multi-modal collaboration among wired and wireless clients.
The tremendous popularity of the Internet has let to the emergence of many applications with widely varying characteristics and requirements. An important class of such applications with high commercial potential is distributed multimedia applications. Video Conferencing, Video-on-Demand and IP telephony are a few of these applications that have evoked much research interest due to the many technical challenges that need to be overcome for successful deployment of these applications in the Internet. These applications have time bounded processing and communication requirements because the coding and compression techniques impose temporal dependencies on media. Typically playback involves reproduction of multiple media in a tightly synchronized manner. This imposes requirement of temporal and spatial guarantees from the underlying network. Traditionally high bandwidth applications such as Video-on-Demand (VoD) requiring transmission of real-time high quality video signals is inhibited by the bandwidth limitation on ‘the last mile’ due to low speed connections used by end user to connect to Internet Service Providers (ISP). However technologies such as cable modem, digital subscriber line (DSL) promise to remove this hurdle and make such applications feasible on the Internet.
Distributed multimedia applications typically operate in heterogeneous environments where the network resources and the end-host processing capabilities vary significantly. Since the network and end host system conditions are dynamic, distributed applications have to contend with unpredictable resource availability. Additionally, the inherent dynamic nature of the resource requirements of these applications makes it very difficult to optimally define the level of service for such applications. Further achieving contracted service is not always practically feasible. However such applications exhibit a common characteristic of operating satisfactorily in less than ideal situations by allowing for a tradeoff between certain service requirements. One approach taken to leverage this property is to employ low bit rate media coding techniques with standard Internet transport protocols. However this does not cater to the time varying nature of the communication channel. Also it does not take care of possible severe degradation in network performance due to potentially misbehaving sources. An alternative approach is to design new transport protocols and use standard media coding algorithms. But this technique cannot utilize the strengths such as compression efficiency, robustness to transmission errors of various coding techniques optimally. Hence to enable operation of these applications with acceptable performance despite potentially insufficient network and end-system resources, runtime adaptation of service is necessary.